Currently, an embodiment of an optical access network in which data is transmitted by an optical fiber in an access line area includes a PON type network. Due to the increase in the speed of data transmission in the access line area, a PON system that realizes a communication speed of 1 Gbps such as a GE-PON (Gigabit Ethernet (registered trademark)-Passive Optical Network), etc., has become widely used.
[Patent document 1] Japanese Patent Application Laid-open 2009-10687